Natural-Uranium Heavy-Water Reactors

McIntyre, H.

doi:10.1038/scientificamerican1075-17

Cited by 22 publications

(5 citation statements)

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“…In the fifties, following a debate on the relative merits of enriched uranium (light water) and natural uranium (heavy water and gas graphite), the journal Nucleonics stated that "to the observer of this debate it seems that enriched reactors must rely heavily upon their development potential to do much better than match the power costs of natural uranium systems." 13 Further, the cost estimates made throughout the fifties, detailed later, by no means pointed to light water as the most efficient technology. 10 When an atom is split, neutrons are released which bombard other atoms, causing them to split and so creating a chain reaction.…”

Section: Cowanmentioning

confidence: 98%

Nuclear Power Reactors: A Study in Technological Lock-in

1990

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ROBIN COWANRecent theory has predicted that if competing technologies operate under dynamic increasing returns, one, possibly inferior, technology will dominate the market. The history of nuclear power technology is used to illustrate these results. Light water is considered inferior to other technologies, yet it dominates the market for power reactors. This is largely due to the early adoption and heavy development by the U.S. Navy of light water for submarine propulsion. When a market for civilian power emerged, light water had a large head start, and by the time other technologies were ready to enter the market, light water was entrenched.

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Section: Cowanmentioning

confidence: 98%

Nuclear Power Reactors: A Study in Technological Lock-in

1990

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“…For example, in most U.S. reactors, the entire core is contained in a single, large pressure vessel, whereas the Candu has its fuel rods encased in individual tubes. Thus, failure of one or more tubes would not be nearly as serious as a break in the single pressure vessel (McIntyre 1975).…”

Section: Turbi Ne Power LI Nesmentioning

confidence: 99%

“…In Canada the reactor used is termed the Candu. "Can" for Canadian, "d" for deuterium oxide (heavy water) which acts as both the moderator and coolant, and "u" is for uranium (McIntyre 1975). In this reactoi:, which has not been completely free of serious problems, the heavywater coolant leaves the reactor at about 310~ (482~ and 1450 pounds per square inch (PSI) pressure, and exchanges this heat to ordinary light water which is converted to steam and used to drive the turbine.…”

Section: Types Of Reactorsmentioning

confidence: 99%

Nuclear energy: Production and problems

Berlyn

Dhillon

Koslow

1980

Environmental Management

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“…This is achieved by the insertion into the reactor core of rods of some such neutron-absorbing material as boron. The boron rods and the driving mechanism which automatically pushes them in and out of the core constitute the control system which sustains the nuclear chain reaction in a steady state (McIntyre, 1975). Many natural systems contain a number of effect0rs, which are brought into operation in series to deal with threats to equilibrium.…”

Section: Restoration Of Equilibriummentioning

confidence: 99%

A cybernetic model for curriculum development

Pratt

1982

Instr Sci

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The task of the curriculum developer is to design instructional systems which will produce consistently high levels of learning despite wide variation in pupil characteristics. This can be viewed as a cybernetic question of regulating variety in a system to produce stable and high level output. Six cybernetic principles -goal orientation, limitation of input, monitoring, control decisions, restoration of equilibrium, and positive feedbackare described, and their application to curriculum discussed. It is concluded thata cybernetic model can guide curriculum developers in designing effective learning systems. Curriculum as an Applied ScienceThe last decade has seen enormous advances in curriculum develoPment. The field is currently characterized by a sense of optimism and confidence which is the more striking when compared with the gloom and defeatism that prevailed in the "schools make no difference" aftermath of the Coleman Report.It is only a decade since Schwab described the curriculum field as moribund, mad ascribed its moribundity to "inveterate, unexamined, and mistaken reliance on theory" (Schwab, 1969: 1). Schwab was half-right. The field of curriculum was not moribund: even as he wrote, the most significant advance of a generation, Mastery Learning, was well under way. But the search for a "curriculum theory" was, as it remains, a false trail. Curriculum, like such applied sciences as engineering or medicine, does not generate theory of its own. Curriculum development is usually pragmatic, discovering by experience what works. Sometimes curriculum derives operating principles from theory in the sciences; more commonly it first develops a practice and subsequently seeks its theoretical basis.Curriculum development -the process of planning instructional systems -has successfully adopted many operating principles from such 0020-4277/82/0000-0000/$2.75 © 1982 Elsevier Scientific Publishing Company fields as philosophy, measurement, and psychology. Cybernetics -which might be defined as the science of self-regulation in systems -has enriched many disciplines, from biology and ecology to political science and psychiatry. But although educators have adopted (somewhat loosely) such cybernetic terms as "feedback", the richness of cybernetics does not appear to have been fully described or utilized in curriculum thought. Yet the central concerns of curriculum developers -how to help all students learn, and how to maximize individual growth -can be viewed as cybernetic questions.This paper will describe six basic principles from cybernetics which have a direct application to curriculum development. They constitute a model which helps to explain the success of certain curriculum practices, and increases the capacity of practitioners to design effective curricula. Cybernetic SystemsBefore examining cybernetic principles, the basic cybernetic model should be described, and one example provided of a cybernetic system. Figure 1 illustrates the cybemetic model in its simplest form, in which there is a control system and ...

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Natural-Uranium Heavy-Water Reactors

Cited by 22 publications

References 0 publications

Nuclear Power Reactors: A Study in Technological Lock-in

Nuclear Power Reactors: A Study in Technological Lock-in

Nuclear energy: Production and problems

A cybernetic model for curriculum development

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